AN Joint Series are composed of flexible joints which meet the earthquake-proof level 2 as stipulated by the earthquake-proof design guideline for sewage work issued by the Japan sewage works Association. As a major feature of the AN Joint Series products, the use of water-swelling sponge, which has been uniquely developed by Nishikawa, can be pointed. Water-swelling sponge located at the joint section has the secondary water sealing effect and prevent any unidentified water from flowing in, resulting in showing the excellent water sealing performance.